1# lseek.m4 serial 4
2dnl Copyright (C) 2007, 2009 Free Software Foundation, Inc.
3dnl This file is free software; the Free Software Foundation
4dnl gives unlimited permission to copy and/or distribute it,
5dnl with or without modifications, as long as this notice is preserved.
6
7AC_DEFUN([gl_FUNC_LSEEK],
8[
9  AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
10  AC_REQUIRE([AC_PROG_CC])
11  AC_CACHE_CHECK([whether lseek detects pipes], [gl_cv_func_lseek_pipe],
12    [if test $cross_compiling = no; then
13       AC_LINK_IFELSE([
14#include <sys/types.h> /* for off_t */
15#include <stdio.h> /* for SEEK_CUR */
16#include <unistd.h>
17int main ()
18{
19  /* Exit with success only if stdin is seekable.  */
20  return lseek (0, (off_t)0, SEEK_CUR) < 0;
21}],
22	 [if test -s conftest$ac_exeext \
23	     && ./conftest$ac_exeext < conftest.$ac_ext \
24	     && { echo hi | ./conftest$ac_exeext; test $? = 1; }; then
25	    gl_cv_func_lseek_pipe=yes
26	  else
27	    gl_cv_func_lseek_pipe=no
28	  fi],
29	 [gl_cv_func_lseek_pipe=no])
30     else
31       AC_COMPILE_IFELSE([
32#if ((defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__) || defined __BEOS__
33/* mingw and BeOS mistakenly return 0 when trying to seek on pipes.  */
34  Choke me.
35#endif],
36	 [gl_cv_func_lseek_pipe=yes], [gl_cv_func_lseek_pipe=no])
37     fi])
38  if test $gl_cv_func_lseek_pipe = no; then
39    gl_REPLACE_LSEEK
40  fi
41])
42
43AC_DEFUN([gl_REPLACE_LSEEK],
44[
45  AC_LIBOBJ([lseek])
46  AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
47  REPLACE_LSEEK=1
48  AC_DEFINE([LSEEK_PIPE_BROKEN], [1],
49	    [Define to 1 if lseek does not detect pipes.])
50])
51